The present invention relates to a method of and an apparatus for motion estimation of video data, and more particularly to a method for compressing video data having a very large quantity of information as in high definition TV (HDTV).
Generally, typical motion estimators for HDTVs developed heretofore utilize a block matching algorithm. Such a block matching algorithm is illustrated in FIG. 1. In accordance with the block matching algorithm, the current frame is divided into smaller rectangular areas, which we call blocks. Each block is shifted to all possible positions within a previously determined window from the previous frame and a mismatch or cost function is computed for each displacement. The displacement that minimizes the cost function determines the motion vectors of the block.
As such a block matching algorithm, there have been proposed various methods. For example, U.S. Pat. No. 4,897,720 discloses a full search block matching algorithm which is capable of minimizing errors, as compared with other methods. Although good in terms of performance, this method is difficult to use in real time processing by use of current techniques. For instance, when a search area for a 8.times.8 block (namely, 8 horizontal pixels .times.8 vertical pixels) is ranged from -32 to +31 in a horizontal direction and from -8 to +7 in a vertical direction, absolute errors are calculated for 64.times.16 (1024) blocks.
At this time, the calculation for each block is achieved by carrying out calculations for 64 pixels, because each block is constituted by 8.times.8 pixels. For achieving the calculation for each pixel, it is required to subtract the pixel value of the previous frame from the pixel value of the current frame and then derive the absolute value of the result of the subtraction. Since this calculation should be repeated 64 times and the search area includes totally 1,024 blocks, the amount of data to be calculated is very large. This makes it difficult to realize a hardware enabling the real time processing by use of current techniques.